import pygame
from pygame.sprite import Group
import sys
from settings import Settings
from ship import Ship
from alien import Alien
from bullet import Bullet
from time import sleep
from button import Button

def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少个外星人"""
    available_space_x = ai_settings.screen_width - 2 * alien_width 
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x 

def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height -
        (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height)) 
    return number_rows 

def create_alien(ai_settings, screen, aliens, alien_number, row_number): 
    """创建一个外星人并将其放在当前行"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number 
    aliens.add(alien)

def fire_bullet(ai_settings,stats, screen, ship, bullets):
    """如果还没有到达限制，就发射一颗子弹"""
    # 创建新子弹，并将其加入到编组bullets中
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet) 
        fire_music(ai_settings,stats)

def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break


def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移，并改变它们的方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1 


def check_keydown_events(event,stats, ai_settings, screen, ship, bullets):
    """响应按键"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings,stats, screen, ship, bullets)
    elif event.key == pygame.K_q:
        print("quit")
        stats.game_active=False
        # sys.exit() 


def check_keyup_events(event, ship):
    """响应松开"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_play_button(ai_settings, screen, stats, sb, play_button, ship,
    aliens, bullets, mouse_x, mouse_y):
    """玩家单击Play按钮时开始新游戏"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:
        # 重置游戏设置
        ai_settings.initialize_dynamic_settings() 
        # 隐藏光标
        pygame.mouse.set_visible(False) 
        # 重置游戏统计信息
        stats.reset_stats()   
        stats.game_active = True 

        # 重置记分牌图像
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_level() 
        sb.prep_ships()   

        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        # 创建一群新的外星人，并让飞船居中
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship() 

def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
    aliens, bullets): 
    """响应子弹和外星人的碰撞"""
    # 删除发生碰撞的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    # 更新现有得分和最高得分
    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)
            sb.prep_score() 
            Sound = pygame.mixer.Sound(ai_settings.boom_music)
            Sound.set_volume(ai_settings.load)
            Sound.play()            
        check_high_score(stats, sb)
    if len(aliens) == 0:
        # 删除现有的所有子弹
        bullets.empty()
        # 提高速度设置和外星人点数
        ai_settings.increase_speed()

        # 提高等级
        stats.level += 1
        sb.prep_level()
        # 创建一个新的外星人群
        create_fleet(ai_settings, screen, ship, aliens) 

def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, 
    bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            # 像飞船被撞到一样进行处理
            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
            break  

def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    # 创建一个外星人，并计算每行可容纳多少个外星人
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    # number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height) 
    number_rows = 1

    # 创建外星人群
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number,row_number) 

def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """响应被外星人撞到的飞船"""
    if stats.ships_left > 0: 
        # 将ships_left减1
        stats.ships_left -= 1

        # 更新记分牌
        sb.prep_ships() 

        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty() 

        # 创建一群新的外星人，并将飞船放到屏幕底端中央
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

        # 暂停
        sleep(0.5)
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)

def check_high_score(stats, sb):
    """检查是否诞生了新的最高得分"""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score() 

def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens,
    bullets):   
    """响应按键和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:                                     # 这里的事件是，下降沿，不是状态量
            check_keydown_events(event,stats, ai_settings, screen, ship, bullets)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(ai_settings, screen, stats, sb, play_button,
                ship, aliens, bullets, mouse_x, mouse_y)  

def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """更新子弹的位置，并删除已消失的子弹"""
    # 更新子弹的位置
    bullets.update() 
 
    # 删除已消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    # 响应子弹和外星人的碰撞
    check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
        aliens, bullets) 

def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets): 
    """
    检查是否有外星人位于屏幕边缘，并更新整群外星人的位置
    """
    check_fleet_edges(ai_settings, aliens)
    aliens.update() 

    # 检测外星人和飞船之间的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets) 

    # 检查是否有外星人到达屏幕底端
    check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets) 

def update_screen(ai_settings,background,screen, stats, sb, ship, aliens, bullets,
    play_button):  
    """更新屏幕上的图像，并切换到新屏幕"""
    # 每次循环时都重绘屏幕
    # screen.fill(ai_settings.bg_color)
    # 加载带有Alpha通道的图像
    screen.blit(background, (0, 0))
    # 在飞船和外星人后面重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()
    # 绘制飞船
    ship.blitme()
    # 绘制外星人
    aliens.draw(screen)       # 对编组调用draw()时，Pygame自动绘制编组的每个元素，绘制位置由元素的属性rect决定
    # 显示得分
    sb.show_score()

    # 如果游戏处于非活动状态，就绘制Play按钮
    if not stats.game_active:
        pygame.mouse.set_visible(True) 
        play_button.draw_button()
    # 让最近绘制的屏幕可见
    pygame.display.flip()

def fire_music(ai_settings,stats):
    sound = pygame.mixer.Sound(ai_settings.bullet_music)
    if(stats.level > 4):
        sound.set_volume(ai_settings.load)
    else:
        sound.set_volume(0.2*stats.level)
    sound.play()
